Dropbox recently announced its new datastore API and it's getting a lot of buzz as an iCloud competitor (specifically the core data sync portion). While it's far less technically advanced than core data syncing (this might be a good thing), it does seem to be going after the same kinds of apps. Does Dropbox have an advantage over iCloud because it doesn't require the app to be sold through the Mac App Store and it works with web apps (and other device types)? Does iCloud have an advantage because every Apple ID customer already has an account? Yes on both ends. I think this is ultimately a win for users as it's competition for Apple's iCloud service. Apple is at its best when it's backed into a corner.
Does it make sense for a developer to trust either system, though? Does it not make sense that the The Omni Group would want to control its own cloud infrastructure (they do) rather than rely on a third party? Shouldn't great developers follow the Cook Doctrine (believing that you need to own and control the primary technologies behind the products you make)?